For the goodbye challenge, jump into the well at seatown (after knifing the chickens.)
Toughest trying to complete, that's easy, bulletproof 3, deflect 50,000 bullets with your riot sheild. This challenge doesn't carry over prestiges and almost noone shoots at you, they try to knife you. I have about 39,000 bullets to go, I should have prestiged about 30-40 hours ago.
Everyone has said it, Seatown, jump in that big big hole aka the well..
Hardest challenges, Riot shield challenges require time, they're easy, but frustrating and slow.
Completed all the Throwing knife and C4 challenges, except the counter C4 where you must kill an enemy by shooting C4, I think there is a loop hole for that.
Also thrown back grenades challenge.
Multikills with Frags, only done the 25 part of it, should get 50 I think.
There are plenty of difficult or time taking challenges to do, the way I've done few that I thought were impossible, were by just playing like a maniac and improvising in most situations, How The? Silence etc.
ahaha today, while playing with Father and Infinitlag, although i think this was before infinitelag joined, I just started blowing up myself up by shooting cars right in front of me cause there was only one or two enemies (dern ragequitters!) and....i forgot my point. it was fun though!
also the perfection challenges seem like the hardest to me, not missing a single shot from a sub/auto/lmg? thats crazy! Sniper one's pretty easy unless you reload all the time like me hahaha
and the crush an enemy with a care package is pretty easy really. Go to Dom and throw it at one of the flags, some people are idiots you'll get one eventually. and if not throw it at a slope so it tumbles down and hopefully crushes someone!
Hardest one has to be the LMG one. I got the one whre you get hurt by and enemy then you backstap them. I was in in the pipe at hardhat trolling with usp tac knife and throwing knife acting like I was playing infected with FATHER and pikaboo. Tryed to knife but knife lunge went past him. Red screen then backstab. Can't remember what the title says though.
Well there are some that are impossible like the LMG Perfectionist (Anarchist? iirc) shooting 50 bullets without missing with an LMG is damn near impossible.
I'd have to say situational challenges where you actually get lucky, ie:
I completed the Dominos and How the Hell? challenges by getting a lucky shot... I saw a claymore near a door so I shot it through the wall it exploded and it killed the player that owned it... he came back because he heard me move up the stairs.. needless to say that was 100% situation related and luck.
Dominos really was completely retarded... lots of players camp on the apartment overlooking the center of the map Lockdown...
and generally they'll lay down 1 claymore each at the wall... so If you spot one just try to make noise or shoot to get on the radar... when they turn close to the wall shoot one of the claymores and it'll make the other one explode getting you the kill.
And earning the Dominos.
Both are kinda tough but not impossible.
The ones that are really cool are, the Think Fast Series.
Getting them is actually pretty fun and cool when you manage to pull one off.
Mainly because you have to shoot and then just humiliate them by throwing a Frag/Stun/Flash at em... So far I've accomplished Frag and Stun... I don't use a lot of flashes but they work exactly the same.
They all take severe skill but are not completely impossible to pull off.
(You can cheat your way into one... stand behind an AFK enemy or Camper... and go prone... shoot em twice with your AR/SUB/Pistol and then throw the grenade... it's cheap and slightly cheating, but it's a way to get it... personally I like the frontal assault... if you pull that one off it's really awesome, because it means the other player got completely outplayed... hitting someone while both are strafing with a Tactical Nade is pretty damn tough.)
I would say the Dictator (full mag no miss with the LMG) would be the toughest. But, the one that keeps drivin me batty is DarkBringer (delete 25 Tac Inserts) in Tactical challenges. The closest I have gotent so far, ironically, was 23 (LOL) before I couldn't take it and prestiged again. Just have to get lucky and find them. I did find a fool who kept putting his Tac Insert in the same corner of the small hut in Outpost yesterday. I kept going back to find it.That got me four that match alone!
Oh, and this prestige I am killing my K/D-R trying for the 1000+ plus kills with the M-16! IMO the most Bi-Polar gun in the game. It can take fools out with one burst, even at range, like a Type 95 or just be a hit marker machine! I guess it depends on the mood it is in at the moment LOL!
Hah, I've gotten into 20 every god damn prestige, I've got accolades, about 70 of them about destroying the freaking flare, but never gotten 25 before I decided to prestige.
Loop hole... I SHALL TRY AND FIND IT, done that with so many challenges
Ever need tips about easy way of doing the challenges, remember to ask and I might be able to tell you the easy way